11.9.26 – Update: Microsoft has finally acknowledged that this is a known issue and engineering teams are working on it.
11.9.26 – Potential Solution: We, and some other industry professionals, have seen that some of the users that receive this error when attempting to email one of the impacted domains do not have DMARC set up properly. We have seen success with working with impacted users to resolve DMARC records to restore communiations.
ORIGINAL STORY
We are seeing reports today from some customers that attempting to email consumer level Outlook/Hotmail/Live email addresses is resulting in an “SPF validation error” or “Auth error.”
Status codes: 550 5.7.23 or similar
After investigating for our customers, we have identified that this a Microsoft issue. It looks like they have made a change on the backend, and this is having a widespread impact.
This issue is impacting random accounts and random emails, so it is intermittent and may not impact your specific account.
Microsoft has not made any communication regarding this issue yet.
We will continue monitor and will update you once we have more information.